1. Field of Invention
The invention relates to a refiner comprising a stator and a rotor, the stator and the rotor comprising a flat portion and a conical portion, the conical portion having a first end of smaller diameter and a second end of greater diameter such that the first end of the conical portion having smaller diameter is directed towards the fiat portion and the second end of the conical portion having greater diameter is directed away from the flat portion, and which flat portion and the conical portion comprise refining surfaces provided with blade to bars and blade grooves therebetween.
The invention further relates to a blade segment of a refiner comprising a stator and a rotor, the stator and the rotor comprising a flat portion and a conical portion, the conical portion having a first end of smaller diameter and a second end of greater diameter such that the first end of the conical portion having smaller diameter is directed towards the flat portion and the second end of the conical portion having greater diameter is directed away from the flat portion, and which blade segment is configurable to form at least part of the refining surface of the conical portion of the stator and which blade segment comprises blade bars and blade grooves therebetween, which together form the refining surface of the blade segment.
Refiners for processing fibrous material typically comprise two, but possibly also more, oppositely situated refining surfaces, at least one of which is arranged to rotate about a shaft such that the refining surfaces turn relative to one another. The refining surfaces of the refiner, i.e. its blade surfaces or the blade set, typically consist of protrusions, i.e. blade bars, provided in the refining surface and blade grooves between the blade bars. Hereinafter, blade bars may also be referred to as bars and blade grooves as grooves. The refining surface often consists of a plural number of juxtaposed blade segments, in which case the refining surfaces of individual blade segments together form an integral, uniform refining surface.
2. Description of Related Art
WO 97/18037 discloses a refiner provided with a stator, i.e. a fixed, immobile refiner element, and a refiner element to be rotated by means of a shaft, i.e. a rotor. Both the stator with its refining surface and the rotor with its refining surface are formed of a flat portion substantially perpendicular to the rotor shaft and a conical portion provided after this fiat portion and arranged at an angle to the flat portion. The conical portion therefore has the first end of smaller diameter and the second end of greater diameter such that the first end of the conical portion having the smaller diameter is directed towards the flat portion of the refiner and the second end of the conical portion having the greater diameter is directed away from the flat portion of the refiner. The flat and conical portions of the stator and the rotor are spaced apart such that a blade gap is formed between the refining surface of the stator and the refining surface of the rotor. The fibrous material to be refined is fed into the blade gap between the fiat portions of the stator and the rotor. As the material to be refined is being processed, it moves forward in the blade gap between the refining surfaces of the flat portion and further into the blade gap between the refining surfaces of the conical portion and finally away from the blade gap.
FIG. 2 is a schematic view of a refining surface of a blade segment for a conical portion of a stator typically used in refiners as disclosed for example in WO 97/18037. The prior art blade segment 19 of FIG. 2 comprises a refining surface 12 having blade bars 20 and blade grooves 21 between the blade bars 20. Between the blade bars 20 there are also dams 26 distributed over the whole refining surface area. The blade bars 20 and the blade grooves 21 have a V-shaped form, making it possible to rotate a rotor of the refiner in both directions and still achieve the similar refining behaviour. The advantage of this is that the rotor of the refiner may be rotated freely in both directions. However, the present use of refiners promotes the rotation of the rotor only in one direction due to the energy consumption and blade set lifetime reasons. In result of this the V-shaped blade bar and blade groove form in the refining surface of the stator is problematic, because one half of the refining surface of the stator feeds the material to be refined out of the blade gap and the other half of the refining surface of the stator prevents the material to be refined moving out of the refiner, what leads to the unhomogeneous pulp quality. The variation of the intersecting angle of the V-shaped blade bars of the stator decreases the loading capacity of the refiner, thus preventing the effective utilization of the refiner.